Why Use Dickow Magnet Drive Pumps?
Since the early Seventies, concern for the environment has become increasingly important in the design of industrial plants. Today, this issue is always paramount in any public discussion involving new plants or the updating of facilities. Accordingly, equipment designers and engineers must offer solutions which will eliminate an adverse impact on the environment or at least reduce it to sustainable levels.

The weakest link with regard to potential environmental damage in the case of centrifugal pumps, is the shaft sealing, because there is always some inherent emission from mechanical seals. Average emission rate of a mechanical seal is 0.13 GPM to 0.35 GPM. While that rate seems insignificant at first glance, the actual atmospheric penetration is very large, indeed, considering that large chemical processing plants have thousands of pumps in operation. In 1989 the Environmental Protection Agency of the U.S. published its first report on environmental pollution. The report documents that the American chemical and petrochemical industries in 1987 emitted 390 tons of toxic materials into the atmosphere, in part attributable to pump leakage.

Potential problems are caused by formation of dangerous explosive mixtures, which become worse when toxic or malodorous gases and vapors endanger maintenance staff. In order to prevent vaporization of liquids between the faces of mechanical seals, additional cooling is required when handling media with vapor pressure above atmospheric pressure at operating temperatures. For handling pumpage which recrystallizes in the atmosphere, an appropriate quench connection or barrier fluid must be provided.

In the past, various attempts were made to improve the performance of mechanical seals and meet anti-pollution requirements. Examples are the double acting mechanical seal of “Tandem Design” and of “Back-to-Back- Design” both with necessary auxiliary equipment. However, for many applications the cost of equipment was not justifiable in light of the gains attained. It would appear that the outer limits have been reached for improvements in mechanical seals with regard to reliability and emissions control.

The only realistic solution is a sealless pump with zero leakage, i.e. without connection between the media and the environment due to the absence of a seal. The use of sealless pumps, especially the magnetic driven pump segment, have grown remarkably in recent years.

Of course sealless magnetically driven pumps have been available since the early 1950s. However, the then available Ferrite and Alnico magnets presented many disadvantages. For example, demagnetization of magnets if the magnet coupling slips due to blocked internal rotor or to overloading; requirement of big magnet masses to transmit rated power for avoiding direct on-line starting; poor efficiency through magnet losses of up to 20% of the rated hydraulic power; and slide bearing problems caused by wear and corrosion.

However, the development of permanent magnets of Rare Earths and Cobalt have made it feasible to design and build a centrifugal pump hermetically sealed, without any shaft duct to the atmosphere. Due to the compact construction, the magnet losses were also reduced, so that coupling efficiencies of more than 90% could be attained. Pumps with such compact permanent magnet couplings can be driven by any standard motor on direct-on-line starting.

Our strong engineering capabilities have made Dickow Pump and industry leader worldwide. New products are continually being developed to suit customer needs.

Dickow Pumps are designed for smooth operation, extended life, and ease of maintenance.